This invention relates generally to blow molding machines and more particularly to an extrusion head of the accumulator type for forming a parison tube having a transparent view stripe in the body of the tube.
Colored plastic containers are generally opaque and therefore the level of contents within the container cannot be directly ascertained when viewed form the outside. One solution is to form the container from clear plastic material and provide a sleeve cover or film of colored material having a thin vertical transparent strip so that the container has what appears to be a clear vertical view stripe in its side. This approach has a disadvantage that the container must have a separately applied colored sleeve or wrapping, which adds to the cost and complicates the production process.
The principal object of this invention therefore is to provide an improved accumulator head which forms a tube with an integral view stripe in a single operation.
The accumulator head utilized in this invention is a modification of a conventional accumulator head. Such an accmulator head having a diverter sleeve to eliminate weld line formation is fully described in U.S. Pat. No. 4,609,340, commonly assigned, and incorporated herein by reference.
The present invention includes the additional feature of a second inlet orifice located between the accumulation chamber and the outlet orifice of the accmulator head for injection of a second plastic material into the flow stream of plastic material being extruded through the outlet orifice whereby the extruded plastic flowing out of the annular outlet orifice forms a tube having an integral vertical stripe composed of the second plastic material.
The injection of the second plastic material through the second inlet orifice is timed to coincide with the discharge of melt from the accumulation chamber.
The result is an improved accumulator head which enables the production of a high quality molded container such as a storage drum having a portion of its wall composed of a different plastic material such as a transparent plastic stripe allowing visual observation of the level of contents within the container.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawing.